Method for opening a proprietary MAC protocol in a non-DOCSIS modem compatibly with a DOCSIS modem

ABSTRACT

A two way communication system is adapted for compatible inter-operation of a plurality of devices operating in accordance with a plurality of protocols. The communication system includes a first group of one or more remote devices that interface with a local host in accordance with a first protocol and a second group of one or more remote devices that interface wit the local host in accordance with a second protocol. The local host includes a protocol processor that identifies transmissions from the first and second groups of remote devices and routes transmissions from the first group of remote devices to a first processor operating in accordance with the first protocol and also routes transmissions from the second group of remote devices to a second processor operating in accordance with the second protocol.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 60/171,912 filed Dec. 23, 1999 the content of which is herebyincorporated by reference.

FIELD OF THE INVENTION

The present invention relates generally to broadband multimedia datadistribution systems, and more particularly, to a method and apparatusfor interfacing non-DOCSIS cable modems with DOCSIS compatible cablemodems.

BACKGROUND

Traditional dial-up modems provide online access through the publictelephone network at up to 56 Kbps (equal to 56,000 bits per second). Acable modem, on the other hand, provides users with high-speed Internetaccess through a cable television network. A cable modem is capable ofproviding data rates as high as 56 Mbps, and is thus suitable for highspeed Internet access, digital television (such as pay-per-view) anddigital telephony.

The Data Over Cable Service Interface Specification (DOCSIS) protocolwas developed to ensure that cable modem equipment built by a variety ofmanufacturers is compatible, as is the case with traditional dial-upmodems. However, DOCSIS compliant systems, as currently defined, do notefficiently transmit many types of data, such as, for example, voice.

Therefore, it would be desirable to provide a method and apparatus foroperating a proprietary MAC protocol in customer premise equipment, suchas, for example, a cable modem, that overcomes the limitations of theDOCSIS protocol, and interoperates with DOCSIS compatible cable modemsresident on the same mixed network.

SUMMARY OF THE INVENTION

In one aspect of the present invention a method for networking a centralcontroller with a first group of one or more remote devices operating inaccordance with a first protocol and a second group of one or moreremote devices operating in accordance with a second protocol, includesidentifying transmissions from said first and second groups of remotedevices, routing transmissions from said first group of remote devicesto a first processor operating in accordance with the first protocolwithin the central controller, and routing transmissions from the secondgroup of remote devices to a second processor operating in accordancewith the second protocol within the central controller.

In another aspect of the present invention a method for networking acable modem termination system with a first group of one or more cablemodems operating in accordance with a proprietary protocol and a secondgroup of one or more cable modems operating in accordance with DOCSISprotocol, includes identifying transmissions from the first group andsecond group of cable modems, routing transmissions from the first groupof cable modems to a first processor that operates in accordance withthe proprietary protocol within the cable modem termination system, androuting transmissions from the second group of cable modems to a secondprocessor that operates in accordance with the DOCSIS protocol withinthe cable modem termination system.

In a further aspect of the present invention, a two way communicationsystem cable of compatible inter-operation of a plurality of devicesoperating in accordance with a plurality of protocols. The communicationsystem includes a first group of one or more remote devices thatinterface with a local host in accordance with a first protocol and asecond group of one or more remote devices that interface wit the localhost in accordance with a second protocol. The local host includes aprotocol processor that identifies transmissions from the first andsecond groups of remote devices and routes transmissions from the firstgroup of remote devices to a first processor operating in accordancewith the first protocol and also routes transmissions from the secondgroup of remote devices to a second processor operating in accordancewith the second protocol.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings where:

FIG. 1 is a schematic diagram of a hybrid fiber coaxial (HFC) networkshowing typical pathways for data transmission between the headend(which contains the cable modem termination system) and a plurality ofhomes (each of which contain a cable modem);

FIG. 2 is a schematic diagram of a cable system having a cable modemoperating in accordance with a proprietary non-DOCSIS compatibleprotocol integrated with DOCSIS compatible cable modem system inaccordance with an exemplary embodiment of the present invention;

FIG. 3 is a system block diagram of an exemplary cable modem terminationsystem capable of supporting device operating in accordance with two ormore protocols in accordance with a preferred embodiment of the presentinvention;

FIG. 4 a is a is a system block diagram of a DOCSIS comaptible cablemodem in accordance with a preferred embodiment of the presentinvention;

FIG. 4 b is a system block diagram of a cable modem operating inaccordance with a proprietary protocol in accordance with a preferredembodiment of the present invention;

FIG. 5 is a flow diagram demonstrating the integration of a non-DOCSIScable modem into a DOCSIS compatible cable modem system in accordancewith an exemplary embodiment of the present invention; and

FIG. 6 is graphical illustration of a MAC frame.

DETAILED DESCRIPTION OF THE INVENTION

An exemplary embodiment of the present invention provides a method foroperating a proprietary media access control (MAC) protocol in anon-DOCSIS cable modem. In the described exemplary embodiment, thenon-DOCSIS cable modem interoperates with DOCSIS compatible cable modemsresident on the same network. The DOCSIS protocol defines a series ofinterface specifications that standardize high speed packet basedcommunications on a cable television system. Compliance with the DOCSISprotocol ensures conforming hardware will interoperate to permittransparent bi-directional transfer of Internet Protocol (IP) traffic,as well as other traffic, between a cable headend and customer premiseequipment over an all-co-axial or hybrid-fiber/coax (HFC) cable network.In order to appreciate the advantages of the present invention, it willbe beneficial to describe the invention in the context of an exemplarybi-directional communication network, such as, for example, a HFCnetwork.

Referring now to FIG. 1, a HFC network facilitates the transmission ofdata between a headend 12, which includes at least one cable modemtermination system, and a number of homes 14, each of which contains acable modem. As used herein, the CMTS is defined to include that portionof a headend which facilitates communication with a plurality of cablemodems. A typical cable modem termination system includes a burstreceiver, a continuous transmitter and a medium access control (MAC) asdisclosed in commonly owned U.S. patent application Ser. No. 09/574,558,entitled “CABLE MODEM APPARATUS AND METHOD”, filed May 19, 2000, nowU.S. Pat. No. 6,650,624, the content of which is incorporated fullyherein by reference. Such hybrid fiber coaxial networks are commonlyutilized by cable providers to provide Internet access, cabletelevision, pay-per-view and the like to subscribers.

Approximately 500 homes 14 are in electrical communication with eachnode 16, 34 of the hybrid fiber coaxial network 10, typically viacoaxial cables 29, 30, 31. Amplifiers 15 facilitate the electricalconnection of the more distant homes 14 to the nodes 16, 34 by boostingthe electrical signals so as to desirably enhance the signal-to-noiseratio of such communications and by then transmitting the electricalsignals over coaxial cables 30, 31. Coaxial cable 29 electricallyinterconnects the homes 14 with the coaxial cables 30, 31, which extendbetween amplifiers 15 and nodes 16, 34. Each node 16, 34 is electricallyconnected to a hub 22, 24, typically via an optical fiber 28, 32. Thehubs 22, 24 are in communication with the headend 12, via optical fibers20, 26. Each hub is typically capable of facilitating communication withapproximately 20,000 homes 14.

The optical fibers 20, 26 extending intermediate the headend 12 and eachhub 22, 24 defines a fiber ring which is typically capable offacilitating communication between approximately 100,000 homes 14 andthe headend 12. The headend 12 may include video servers, satellitereceivers, video modulators, telephone switches and/or Internet routers18, as well as the cable modem termination system. The headend 12communicates via transmission line 13, that may be a T1 or T2 line, withthe Internet, other headends and/or any other desired device(s) ornetwork.

An exemplary embodiment of the present invention allows a single CMTS tosupport on-line and off-line bidirectional communication betweennon-DOCSIS cable modems as well as between DOCSIS compatible cablemodems and a variety of far end data termination devices. An exemplarytopology is shown in FIG. 2, wherein a DOCSIS compatible cable modem 110provides an interface to HFC network 100 a for a fax machine 120 a,telephone 122 a and modem 124 a through a subscriber loop interfacecircuit (SLIC) 130 a. A non-DOCSIS cable modem 140 may also provide aninterface to the HFC network 100 a for a fax machine 120 b, a telephone122 b and a modem 124 b or other telephony, multi-media or computingdevices through a subscriber loop interface circuit (SLIC) 130 b. Alocal area network (LAN) 132 a, 132 b and a universal synchronous bus(USB) 134 a, 134 b may also be provided access to the HFC network 100 avia the DOCSIS and non-DOCSIS cable modems respectively.

The near-end HFC network 100 a is coupled to a CMTS line card 142 in theheadend 112. The CMTS line card 142 is coupled to a packet based networkrouter 144 to determine whether the communication will be transportedvia a far end HFC network 100 b, a far end PSTN network 150 or theInternet. In the case of communications over a far end PSTN network aPSTN gateway 152 provides an interface between a far end datatermination device 156 a and the PSTN network 150 connected to theheadend 112.

In the case of a far end HFC network 100 b, a cable modem, such as, forexample, a non-DOCSIS cable modem 140 b, provides an interface between afar end data termination devices 156 b and the far end HFC network 100 bconnected to the headend 112. As those skilled in the art willappreciate, the far end data termination devices 156 a and 156 b mayinclude a variety of telephony and data devices including a telephone,fax machine, and modem via a SLIC or audio processor, as well as a LANor USB.

The packet based network router 144 facilitates communication betweenthe near end data devices and off-line far end data terminating devices156 a via a circuit switched network such as the public switchedtelephone network (PSTN) 150 and the PSTN gateway 152. Data terminationdevices include by way of example, analog and digital phones, ethernetphones, Internet Protocol phones, fax machines, data modems, cablemodems, interactive voice response systems, PBXs, key systems, and anyother conventional telephony devices known in the art. One skilled inthe art will appreciate that the described method of interfacing devicesoperating in accordance with different protocols is not limited to cablemodems on a HFC network. Rather the present invention may be used tointerface network gateways, set top boxes or other multimedia devices ona mixed network. Therefore, the described hybrid fiber coaxial network100 a is by way of example and not a limitation.

The multimedia cable network system (MCNS) DOCSIS radio frequencyinterface specification (SP-RFI-I02-971008) protocol specifies atime-division multiple access (TDMA) protocol for the upstreamtransmission of data packets from cable modems to a cable modemtermination system. In order to accomplish TDMA for upstreamcommunication, it is necessary to assign time slots within which cablemodems having a message to send to the cable modem termination systemare allowed to transmit. The CMTS assigns time slots in accordance withrequests that are placed in a request contention area in the upstreamdata path.

The CMTS responds to such requests from the cable modems with a logicalmessage (MAP) that is broadcast to all of the cable modems on aparticular frequency channel. The MAP message specifies the upstreamframing structure, so as to provide individual time slots within whicheach cable modem may transmit. The MAP specifies which cable modems maytransmit, when they may transmit, and how, e.g., what modulation typethey may utilize to transmit.

Each cable modem is typically identified by one or more station orservice identifiers (SID). The MAP message specifies which SID or cablemodem has control of upstream communications on a particular frequencychannel during each TDMA time slot. The MAP message also specifies thetime at which the time slot begins and which interval usage code orburst type is to be used. When the appropriate TDMA time slot arrives(in time) a cable modem sends a burst of information, e.g., a frame ofvoice or data, to the cable modem termination system.

In accordance with the DOCSIS time-division multiple access protocol,all devices (DOCSIS compatible or otherwise) operating on a DOCSISnetwork simultaneously receive MAP messages and broadcast requests inthe request contention region. Thus, to compatibly interoperate on ashared access network with DOCSIS compatible devices, a device operatingaccording to a non-DOCSIS proprietary protocol must not interfere withthe correct operation of the DOCSIS compatible devices (e.g. cablemodems and CMTS). In addition, communications between DOCSIS compatibledevices preferably do not interfere with the correct operation of adevice operating in accordance with a non-DOCSIS protocol.

Therefore, upstream communications on a mixed network that originatefrom a device operating in accordance with a non-DOCSIS protocol arepreferably distinguished from communications that originate from DOCSIScompatible devices. In operation, the CMTS may therefore identify anddirect upstream non-DOCSIS transmissions to a compatible processing unitin the CMTS and DOCSIS transmissions to a DOCSIS compatible processingunit in the CMTS. Further in the downstream direction, a CMTS ispreferably able to communicate with a specific non-DOCSIS device or allnon-DOCSIS devices such that the communications will be ignored ordiscarded by the DOCSIS compatible devices. Similarly, downstreamcommunications from the CMTS to DOCSIS compatible devices are preferablyignored or discarded by the non-DOCSIS devices.

Referring to FIG. 3, cable modem termination system 142 includes adownstream modulator 200 for transmitting information such as, forexample voice, data, control or service messages to the cable modems andan upstream demodulator 202 for receiving communications from the cablemodems. Downstream modulator 200 may utilize, for example, 64 QAM or 256QAM in a frequency band in the range of 54 to 860 MHz to provide a datarate of up to 56 Mbps. Upstream demodulator 202 may use either QPSK or16 QAM, in a frequency range of 5 MHz to 42 MHz, to provide a data rateof up to 10 Mbps.

In the described exemplary CMTS, a MIPS core 240 in conjunction with itsresident SRAM 250 and external memory 252, provide contention resolutionand scheduling functions to maximize the efficiency of the network byadjusting the number of time slots in accordance with network trafficpatterns. The MIPS core also directs data traffic on bus 254.Furthermore, much of the data transmitted and received by the CMTSrequires extensive processing and formatting. The MIPS core 240 isresponsible for this processing and formatting. For example, the MIPScore manages the conversion of data between 64-QAM, QPSK, and thedigital packet format of the router interface. Further, MIPS core 240interprets management messages and provides basic database managementfunctions.

In the described exemplary embodiment, a protocol processor 210 controlsthe interface between the physical layer (i.e. upstream demodulator anddownstream modulator) and DOCSIS compatible and non-DOCSIS compatiblemedia access controllers 220 and 222 respectively. The protocolprocessor 210 identifies DOCSIS compatible upstream and downstreamcommunications and routes them to the DOCSIS MAC 220 for processing.Likewise the protocol processor 210 identifies non-DOCSIS compatibleupstream and downstream communications and routes them to the non-DOCSISMAC 222 for processing.

Media access controllers (MAC) 220 and 222 encapsulate data receivedfrom a data network interface with the appropriate MAC address of thecable modems on the system. Each cable modem on the system (not shown)has its own MAC address. Whenever a new cable modem is installed, itsaddress is registered with the CMTS. The MAC address is necessary todistinguish upstream data from the cable modems since all the modemsshare a common upstream path, and so that the CMTS transmits downstreamcommunications to the proper cable modem. Thus, each data packet,regardless of protocol, is mapped to a particular MAC address.

A DOCSIS and non-DOCSIS cable modem are shown schematically in FIGS. 4aand 4 b respectively. The DOCSIS cable modem provides a DOCSIScompliant, single chip solution, as disclosed in commonly owned U.S.patent application Ser. No. 09/548,400, entitled “GATEWAY WITH VOICE”filed Apr. 13, 2000, now U.S. Pat. No. 6,765,931, the contents of whichare incorporated herein by reference as if set forth in full. The DOCSIScable modem 110 provides integrated functions for communicating with farend devices via the CMTS (not shown). The non-DOCSIS cable modem 140 mayoperate in accordance with a non-DOCSIS compliant proprietary protocolas described in commonly owned U.S. patent application Ser. No.09/427,792, entitled “SYSTEM AND METHOD FOR MULTIPLEXING DATA FROMMULTIPLE SOURCES”, filed Oct. 27, 1999, now U.S. Pat. No. 6,804,251, thecontents of which are incorporated herein by reference as if set forthin full.

The DOCSIS cable modem 110 and the non-DOCSIS cable modem 140 mayutilize common PHY elements. For example, QPSK upstream modulators 300a, 300 b may be used to transmit data to a far end data terminatingdevice and QAM downstream demodulators 302 a, 302 b may receive datafrom the far end data terminating device via the CMTS. However, upstreammodulator 300 a and downstream demodulator 302 a in the DOCSIS cablemodem 110, interface with a DOCSIS MAC 304, while upstream modulator 300b and downstream demodulator 302 b in the non-DOCSIS cable modem 140interface with a non-DOCSIS MAC 310.

DOCSIS MAC 304 implements the downstream portions of the DOCSISprotocol. DOCSIS MAC extracts DOCSIS MAC frames from MPEG-2 frames,processes MAC headers, and filters and processes messages and data.Downstream data packets and message packets may then be placed in systemmemory 320 via an internal system bus (ISB). DOCSIS MAC 304 andnon-DOCSIS MAC 310 also control the upstream transmission parameters andencapsulate data received from peripheral signal sources with theappropriate header information including a service identifier(SID).

Cable modems 110 and 140 may accept information packets from a pluralityof signal sources. For example, universal serial bus (USB) transceivers322 a, 322 b and USB MACs 324 a, 324 b provide transparent,bi-directional IP traffic between devices operating on a USB such as forexample a PC workstation, server printer or other similar devices andthe far end data terminating device. Additionally, an I.E.E.E. 802.3compliant media independent interface (MII) 330 a, 330 b in conjunctionwith an Ethernet MAC 332 a, 332 b may also be included to providebi-directional data exchange between communications devices such as, forexample a number of PCs and or Ethernet phones and the far end dataterminating device.

In the described exemplary cable modems 110 and 140, a MIPS core 360 a,360 b in conjunction with resident SRAM 320 a, 320 b, manages theconversion of data between 64-QAM, QPSK, and the digital packet formatof the various peripheral devices. Further, MIPS core 360 interpretsmanagement messages and provides basic database management functions.

Cable modems 110, 140 may further include an internal audio processor370 a,370 b with an analog front end 372 a,372 b that interface a voiceprocessor 374 a,374 b with external subscriber line interface circuits(SLICS) 376 a,376 b for bi-directional exchange of voice signals. Thevoice processor 374 a,374 b includes an encoder and decoder system (notshown) that may provide, for example, delay compensation, voice encodingand decoding, DTMF generation and detection, call progress tonegeneration and detection, comfort noise generation and lost framerecovery.

The audio processor 370 a,370 b may include programable elements thatimplement filters and other interface components for a plurality ofvoice channels. In the transmit mode the analog front end 372 a,372 baccepts an analog voice signal from SLIC 376 a, 376 b, digitizes thesignal and forwards the digitized signal to the audio processor 370.

The audio processor 370 a,370 b decimates the digitized signal andconditions the decimated signal to remove far end echos. As the nameimplies, echos in telephone systems is the return of the talker's voiceresulting from the operation of the hybrid with its two-four wireconversion. The audio processor 370 a,370 b can apply a fixedgain/attenuation to the conditioned signal and forwards the gainadjusted signal to the voice processor 374 a,374 b via the PCMinterface. In the receive mode the audio processor accepts a voicesignal via a PCM interface from the voice processor and applies a fixedgain/attenuation to the received signal. The gain adjusted signal isthen interpolated from 8 kHz to 96 kHz before being D/A converted forcommunication via a SLIC interface to a telephony device.

In one embodiment, non-DOCSIS MAC 310 may implement a proprietaryprotocol that provides for efficient multiplexing of voice and data forbi-directional communication over the HFC network. The non-DOCSIS cablemodem may evaluate the relative efficiency of data transmission for agiven grant region given the information packets currently waiting to betransmitted. The non-DOCSIS cable modem preferably evaluates therelationship between signal sources, the size of a packet relative tothe size of the grant region, transmission priorities, and otherknowledge regarding the data packets and the state of the network.Further, to maximize efficiency, the cable modem may concatenate orfragment information packets. In one embodiment, information packetsfrom any signal source may be concatenated with information from anyother, and transmitted within the same grant region. Further, thedescribed exemplary non-DOCSIS cable modem may transmit an informationpacket or fragment thereof in a grant region assigned to differentinformation packet.

Referring to FIG. 5, the CMTS identifies and processes upstreamcommunications from, and downstream communications to, the DOCSIS andnon-DOCSIS cable modems. In one embodiment, service identifiers (SIDs)in the frame header of upstream communications may in part serve toidentify DOCSIS compatible and non-DOCSIS compatible devices. A MACframe is the basic unit of transfer between the MAC sublayers at theCMTS and the cable modems. The same basic structure is used in both theupstream and downstream directions. A MAC frame comprises a MAC headerthat identifies the content of the MAC frame and an optional packet dataunit (PDU).

MAC headers comply with the header format illustrated in FIG. 6.Generally the MAC headers include a frame control field (FC) 500 thatidentifies the type of MAC header, as well as a MAC control field 510,an optional extended header field 520 and a header check sequence 530 toensure the integrity of the MAC header. Broadly speaking there are twotypes of frames transmitted on the upstream channel by the cable modemsto the CMTS. Namely, contention minislot requests that include one ormore SIDs 540 in the header structure and all other types of frames thattypically do not include a service identifier but rather include thelength 550 of the MAC frame.

In an exemplary embodiment of the present invention, each device on thenetwork is initially assigned a primary service identifier (PSID), thatserves to identify the traffic characteristics and schedulingrequirements for that cable modem. In addition, each device is alsoassigned additional SIDs identifying the device as being DOCSIScompatible or non-DOCSIS compatible. The DOCSIS and non-DOCSIS MACs ofthe cable modems embed the additional SIDs in each contention minislotframe. The protocol processor in the CMTS may then identify requestsfrom DOCSIS and non-DOCSIS compatible devices in accordance with theembedded SIDs.

Referring back to FIG. 5, in operation, the CMTS may therefore directrequests in the contention request region from devices having non-DOCSIScompatible SIDs to a corresponding non-DOCSIS processor within the CMTS410. Similarly, the CMTS may direct requests from devices having DOCSIScompatible SIDs to a corresponding DOCSIS processor within the CMTS 420.The CMTS may then appropriately respond to such requests with a grant ofbandwidth during which the cable modems may transmit 424. In addition,in the described exemplary embodiment, collisions between two or morepackets at the CMTS are ignored having no effect on CMTS processing.

However, in the grant region cable modems transmit transport frames onthe upstream channel that do not have a SID embedded in the frameheader. Rather, the SID field is replaced by a field identifying thelength of the packet data unit. Therefore, the CMTS can not directlyidentify the cable modem that transmitted a particular frame byexamining that frame. However, upstream transmissions that do not have aSID field are transmitted in accordance with a minislot assignment fromthe CMTS. The scheduler in the MIPS core of the CMTS therefore knows apriori which device transmitted each frame in a particular set ofminislots. Thus, the CMTS may also identify upstream communications inthe grant region transmitted by both DOCSIS compatible and noncompatible devices.

In operation, the CMTS may therefore direct upstream communications inthe grant region from non-DOCSIS compatible devices to a correspondingnon-DOCSIS processor within the CMTS. Similarly, the CMTS may directupstream communications in the grant region from DOCSIS compatibledevices to a corresponding DOCSIS processor within the CMTS. Theappropriate processor within the CMTS therefore processes upstreamcommunications in the grant region and forwards those communications tothe addressed far end device 424. The CMTS may therefore insulate eachupstream communication from potential interference from a non-compatibledevice. The grant region of the upstream allocated to non-DOCSIS devicesis not mapped by the DOCSIS system mapper.

In the downstream direction the DOCSIS protocol requires thecommunication of a single broadcast messages, such as, for example, MAPmessages, to each device on the network. To comply with this requirementa CMTS in a system having groups of devices operating in accordance withtwo or more different protocols may utilize the DOCSIS multicastmechanism to communicate with each device in a particular group. Forexample, the CMTS may first create a multicast group for the cablemodems operating in accordance with each different protocol 440. TheCMTS may then communicate with a group of devices operating inaccordance with a particular protocol by transmitting a packet using amulticast group 450 that includes each device within that group.

In the described exemplary embodiment, multicast packets addressed tonon-DOCSIS compatible devices conform with the requirements for a DOCSISmulticast packet so as not to produce an error condition in a DOCSIScompatible device. Multicast communications addressed to non-DOCSIScompatible groups however, are ignored by DOCSIS compatible devicessince they are not part of the multicast group. Similarly, multicastpackets addressed to a group of DOCSIS compatible devices will beignored by non-DOCSIS devices that are not part of the multicast group.

In the described exemplary embodiment, downstream communications with agroup of non-DOCSIS compatible devices may be done in the payload of themulticast frame. For example, control information intended for a groupof non-DOCSIS devices may be transmitted to that group in the payload ofa multicast frame. Similarly, the payload of a non-DOCSIS multicastframe may be used to transmit MAP messages downstream to allocateupstream capacity to devices within the non-DOCSIS compatible group.

Further, the CMTS may correlate the destination address of far endcommunications with the protocol of the addressed device 460. The CMTSmay therefore, route far end communications to the appropriate processorwithin the CMTS for processing in accordance with the protocol of theaddressed device. The CMTS may then forward the processed downstreamcommunication having a unicast MAC address to the downstream modulatorfor communication to the individual addressed device 470. Downstreamunicast communications are therefore ignored by all other devices. Thus,the CMTS may also communicate downstream with individual devicesoperating in accordance with a non-DOCSIS protocol without interferingwith the operation of DOCSIS compatible devices on the same mixednetwork. Therefore, a bi-directional communication network operating inaccordance with the present invention may support devices operating inaccordance with a plurality of protocols for efficient utilization ofnetwork bandwidth.

Although a preferred embodiment of the present invention has beendescribed, it should not be construed to limit the scope of the appendedclaims. Those skilled in the art will understand that variousmodifications may be made to the described embodiment. Moreover, tothose skilled in the various arts, the invention itself herein willsuggest solutions to other tasks and adaptations for other applications.It is therefore desired that the present embodiments be considered inall respects as illustrative and not restrictive, reference being madeto the appended claims rather than the foregoing description to indicatethe scope of the invention.

1. A method for networking a central controller with a first group ofone or more remote devices operating in accordance with a first protocoland a second group of one or more remote devices operating in accordancewith a second protocol, comprising: assigning one or more time slots onthe same logical upstream channel during which said first group andsecond group of remote devices may transmit information to said centralcontroller; distinguishing transmissions from said first group of remotedevices from transmissions from said second group of remote devicesbased on said time slot assignments; routing said transmissions fromsaid first group of remote devices to a first processor operating inaccordance with said first protocol within said central controller;routing said transmissions from said second group of remote devices to asecond processor operating in accordance with said second protocolwithin said central controller; wherein said assigning includestransmitting a first group message from said central controller to saidfirst group of remote devices via a first multicast transmission andtransmitting a second group message from said central controller to saidsecond group of remote devices via a second multicast transmission. 2.The method of claim 1, further comprising: embedding a first identifierin transmissions from said first group of remote devices; and embeddinga second identifier in transmissions from said second group of remotedevices, wherein said transmissions from said first and second groups ofremote devices are distinguished in accordance with said first andsecond identifiers.
 3. The method of claim 2, wherein said transmissionsfrom said first and second groups of remote devices comprise bandwidthrequests transmitted in a contention request region.
 4. The method ofclaim 3, further comprising transmitting bandwidth grants to said firstand second groups of remote devices in response to said bandwidthrequests.
 5. The method of claim 1, further comprising: receivingcommunications addressed for said first group and second group of remotedevices; routing communications addressed for said first group of remotedevices to said first processor within said central controller; routingcommunications addressed for said second group of remote devices to saidsecond processor within said central controller; and transmitting theprocessed communications to the addressed remote devices.
 6. The methodof claim 1, wherein said distinguishing step comprises distinguishingtransmissions in a grant region from said first group of remote devicesfrom transmissions in the grant region from said second group of remotedevices based on said time slot assignments.
 7. A method for networkinga cable modem termination system with a first group of one or more cablemodems operating in accordance with a proprietary protocol and a secondgroup of one or more cable modems operating in accordance with a DOCSISprotocol, comprising: assigning one or more time slots on the samelogical upstream channel during which said first group and second groupof cable modems may transmit information to said cable modem terminationsystem; distinguishing transmissions from said first group of cablemodems from transmissions from said second group of cable modems basedon said time slot assignments; routing said transmissions from saidfirst group of cable modems to a first processor that operates inaccordance with said proprietary protocol within said cable modemtermination system; routing said transmissions from said second group ofcable modems to a second processor that operates in accordance with theDOCSIS protocol within said cable modem termination system; wherein saidassigning includes transmitting a first group message from said cablemodem termination system to said first group of cable modems via a firstmulticast transmission and transmitting a second group message from saidcable modem termination system to said second group of cable modems viaa second multicast transmission.
 8. The method of claim 7, furthercomprising: embedding a first identifier in transmissions from saidfirst group of cable modems; and embedding a second identifier intransmissions from said second group of cable modems, wherein saidtransmissions from said first group and second group of cable modems aredistinguished in accordance with said first and second identifiers. 9.The method of claim 8, wherein said transmissions from said first andsecond groups of cable modems comprise bandwidth requests transmitted ina contention request region.
 10. The method of claim 9, furthercomprising transmitting bandwidth grants to said first and second groupsof cable modems in response to said bandwidth requests.
 11. The methodof claim 7, further comprising: receiving communications addressed forsaid first group and second group of cable modems; routingcommunications addressed for said first group of cable modems to saidfirst processor within said cable modem termination system; routingcommunications addressed for said second group of cable modems to saidsecond processor within said cable modem termination system; andtransmitting the processed communications to the addressed cable modems.12. The method of claim 7, wherein said distinguishing step comprisesdistinguishing transmissions in a grant region from said first group ofcable modems from transmissions in the grant region from said secondgroup of cable modems based on said time slot assignments.
 13. A two waycommunication system comprising: a first group of one or more remotedevices that communicate with a local host in accordance with a firstprotocol; and a second group of one or more remote devices thatcommunicate with said local host in accordance with a second protocol,wherein said local host assigns one or more time slots on the samelogical upstream channel during which said first and second groups ofremote devices may transmit information to said local host, wherein saidlocal host comprises a protocol processor for distinguishingtransmissions from said first group of remote devices from transmissionsfrom said second group of remote devices based on said time slotassignments, wherein said protocol processor routes said transmissionsfrom said first group of remote devices to a first processor operatingin accordance with the first protocol and routes said transmissions fromsaid second group of remote devices to a second processor operating inaccordance with the second protocol; wherein said local host assignssaid one or more time slots by transmitting a first group message tosaid first group of one or more remote devices via a first multicasttransmission and transmitting a second group message to said secondgroup of one or more remote devices via a second multicast transmission.14. The two way communication system of claim 13, wherein said localhost further comprises a central processor for scheduling saidtransmissions from said first and second groups of remote devices. 15.The two way communication system of claim 13, wherein said local hostfurther comprises: an upstream demodulator for receiving saidtransmissions from said first and second groups of remote devices; and adownstream modulator for transmitting information to said first andsecond groups of remote devices.
 16. The two way communication system ofclaim 15, wherein each of said remote devices comprises: a downstreamdemodulator for receiving transmissions from said local host; and anupstream modulator for transmitting information to said local host. 17.The two way communication system of claim 16, wherein each of saidremote devices further comprises a media access controller for embeddingservice identifiers in each upstream bandwidth request, wherein saidmedia access controller embeds a first service identifier for said firstgroup of remote devices and a second service identifier for said secondgroup of remote devices.
 18. The two way communication system of claim17, wherein said local host distinguishes transmissions in a requestcontention region from said first group of remote devices fromtransmissions in the request contention region from said second group ofremote devices in accordance with said first and second identifiers. 19.The two way communication system of claim 13, wherein said transmissionsfrom said first and second groups of remote devices comprisetransmissions in a grant region.
 20. A cable television system,comprising: a first group of one or more cable modems that communicatewith a cable modem termination system in accordance with a proprietaryprotocol; and a second group of one or more cable modems thatcommunicate with said cable modem termination system in accordance witha DOCSIS protocol, wherein said cable modem termination system assignsone or more time slots on the same logical upstream channel during whichsaid first and second groups of cable modems may transmit information tosaid cable modem termination system, wherein said cable modemtermination system comprises a protocol processor for distinguishingtransmissions from said first group of cable modems from transmissionsfrom said second group of cable modems based on said time slotassignments, and wherein said protocol processor routes saidtransmissions from said first group of cable modems to a first processoroperating in accordance with the proprietary protocol and routes saidtransmissions from said second group of cable modems to a secondprocessor operating in accordance with the DOCSIS protocol; wherein saidcable modem termination system assigns said one or more time slots bytransmitting a first group message to said first group of one or morecable modems via a first multicast transmission and transmitting asecond group message to said second group of one or more cable modemsvia a second multicast transmission.
 21. The cable television system ofclaim 20, wherein said transmissions from said first and second groupsof cable modems comprise transmissions in a grant region.
 22. The cabletelevision system of claim 20, wherein said cable modem terminationsystem further comprises a central processor for scheduling saidtransmissions from said first and second groups of cable modems inresponse to bandwidth requests from said first and second groups ofcable modems.
 23. The cable television system of claim 20, wherein saidcable modem termination system further comprises: an upstreamdemodulator for receiving said transmissions from said first and secondgroups of cable modems; and a downstream modulator for transmittinginformation to said first and second groups of cable modems.
 24. Thecable television system of claim 23, wherein each of said cable modemscomprises: a downstream demodulator for receiving transmissions fromsaid cable modem termination system; and an upstream modulator fortransmitting information to said cable modem termination system.
 25. Thecable television system of claim 24, wherein each of said cable modemsfurther comprises a media access controller for embedding serviceidentifiers in each upstream bandwidth request, wherein said mediaaccess controller embeds a first service identifier for said first groupof cable modems and a second service identifier for said second group ofcable modems.
 26. The cable television system of claim 25, wherein saidcable modem termination system distinguishes transmissions in a requestcontention region from said first group of cable modems fromtransmissions in the request contention region from said second group ofcable modems in accordance with said first and second identifiers.